In optical telecommunications systems, it is often necessary to distribute a single light signal from one or more optical fibers between a plurality of other optical fibers. Important considerations for a device performing such a function include obtaining as many distribution paths as possible, and its insertion losses.
U.S. Pat. No. 4,285,570 describes one type of light energy distributing device using optical fibers. This device employs a self-focusing lens of the SELFOC (registered trademark) type comprising a bar of refractive material such as glass, for example, having an index gradient therein. In said device, a plurality of optical fibers which are fixed side-by-side to one another are coupled to a first face of a lens, and a reflective coating is deposited on a second face of the lens opposite to the first face. One of said fibers constitutes an inlet fiber and conveys an incident light wave which penetrates into the lens and propagates therethrough. After reflection on said second face of the lens, the light beam leaves the lens through its first face and is thus distributed amongst the other fibers which constitute outlet fibers.
However, such a light energy distribution device possesses several drawbacks. Firstly, since the inlet fiber is located on the same side of the lens as the outlet fibers, a portion of the light energy leaving the lens also enters into the inlet fiber, thus constituting a light "echo" to the inlet fiber which causes disturbances therein. Secondly, this device suffers from numerous Fresnel losses as the fiber/lens interface and also at the covering on the second face of the lens. Further, the number of outlet or distribution paths is limited by the size of the cross-section of the lens, and finally maximal coupling between the fibers and the lens is difficult to achieve.
Preferred embodiments of the present invention remedy these drawbacks by providing a device enabling a single light signal from an inlet optical fiber to be distributed over a large number of outlet optical fibers, and with the inlet fiber being completely isolated from the outlet fibers.